In the past, as an inner seal for sealing an opening of a container in the inside of a cap, a seal film (inner seal member) having a diameter substantially equal to an outer diameter of the opening was widely used. As a handle portion used for peeling off the seal film at an opening time, there is known a technology in which an outer peripheral edge of the seal film is allowed to protrude in a cylindrical shape or a tongue-piece shape so as to use a portion protruding from the opening of the container as the handle portion.
In the case where the outer peripheral edge of the seal film is used as the handle portion, if a dimension of the handle portion is set to be large in order to easily grip the handle portion, the handle portion may be interposed between the container and the cap upon closing the cap on the opening of the container, which may cause an erroneous cap mounting state.
For this reason, there are proposed technologies in which the film is interfolded or adhered so that the handle portion does not protrude in the transverse direction from the opening of the container, but protrudes upward. For example see WO90/09932, WO00/66453, Japanese Patent Application No. 2002-179124 and WO89/02402.
In addition, there is known a technology in which a different member (tab liner layer) is inserted between an upper surface layer and a lower surface layer of the seal film, and the upper surface layer and the lower surface layer are adhered to each other at a position without the different member so that the handle portion formed by the tab liner layer and the upper surface layer does not protrude in the transverse direction from the opening of the container. For Example see Japanese Patent Publication No. H06-99912.